Histidine derivatives

ABSTRACT

THE INVENTION RELATES TO A NOVEL DERIVATIVE OF HISTIDINE OF FORMULA:   N-(CYCLOPENTYL-CO-HIS-)-PYRROLIDINE   IN WHICH HIS L-HISTIDYL, AND ITS PHAARMACEUTICALLY ACCEPTABLE SALTS. THE NOVEL COMPOUND AND ITS SALTS WITH PHARMACEUTICALLY ACCEPTABLE ACIDS ARE USEFUL BECAUSE OF THEIR INHIBITING ACTION ON THE HYPOTHALAMIC THYROTROPIN RELEASING HORMONE (TRH).

3,833,604 HISTIDINE DERIVATIVES Derek John Schafer, Beverley, England, assignor to Reckett & Colman Products Limited, Hull, Yorkshire,

England No Drawing. Filed Jan. 9, 1973, Ser. No. 322,124 Claims priority, application Great Britain, Jan. 20, 1972,

Int. Cl. C07d 49/36 US. Cl. 260-309 3 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a novel derivative of histidine of formula:

([f-His-b/W in which His is L-histidyl, and its pharmaceutically acceptable salts.

The novel compound and its salts with pharmaceutically acceptable acids are useful because of their inhibiting action on the hypothalamic thyrotropin releasing hormone (TRH).

' This invention relates to a derivative of histidine and to processes for its preparation. The invention also relates to therapeuticcompositions comprising as the active ingredient this histidine derivative.

According to this invention there is provided a compound of the formula,

I NH N..

which is conventionally represented as in which His is L-histidyl, and salts with pharmaceutically acceptable acids.

The invention also provides therapeutic compositions comprising as active ingredient the compound of formula I or a salt with a pharmaceutically acceptable acid in association with a pharmaceutically acceptable diluent or carrier.

The compound of the present invention inhibits the action of the hypothalamic thyrotropin releasing hormone I "United States Patent 0 3,833,604 Patented Sept. 3, 1974 'ice thydroidism, the treatment of non-toxic goitres, the prethydroidism and in the treatment of TSH-dependent carcinomas.

The compound of formula I may be prepared by coupling by standard techniques of peptide chemistry a compound of formula II in which R is any group commonly used for the formation of peptide bonds such as azide, chloride, or substituted phenoxy (e.g. p-nitrophenoxy or pentachlorophenoxy) or hydroxy with a compound of formula III III When R is hydroxy the coupling is carried out in the presence of a coupling agent such as dicyclohexylcarbodiirnide.

I-Histidyl pyrrolidine of formula III may be prepared by reacting pyrrolidine either with Z-His-OH (where Z is an N-protecting group commonly used in peptide chemistry such as t-butoxy carbonyl or benzyloxycarboxy) in the presence of dicyclohexylcarbodiimide, or with Z- His-X (where X is a reactive group such as azide or substituted phenoxy), followed by the removal of the N- protecting group. The benzyloxycarbonyl group may be removed by catalytic hydrogenation or using hydrogen bromide in acetic acid and the t-butoxycarbonyl group may be removed using hydrogen chloride in an organic solvent or using anhydrous trifluoracetic acid.

Alternatively the compound of formula I may be prepared by coupling by standard techniques of peptide chemistry a compound of formula II in which R is as hereinbefore defined with a compound of formula IV HHisR' in which R is hydroxy or alkanoxy such as lower alkoxy,

phenoxy or benzyloxy, provided that R' may not be hy-.

droxy when R is hydroxy, to form a compound of formula V N- (Cyclopentylcarbonyl-L-histidy) -pyrrolidine (cpc-His-pyr) (i) N (Benzyloxycarbonyl-L-histidyl)pyrrolidine.-A solution of benzyloxycarbonyl-L-histidine azide in ethyl acetate ml.), prepared from the hydrazide (3.03 g.), was added at 0 C. to pyrrolidine (1.24 ml.). The mixture was kept at 0 C. for 3 /2 hours, evaporated, the residue dissolved in 1N hydrochloric acid ml.) and the solution washed with ether. Excess solid sodium hydrogen carbonate was added, the product extracted into ethyl acetate, the combined extracts dried (Na SO and evaporated giving crude crystalline product (2.3 g.). Recrystallisation from ethyl acetate/ethanol gave the desired product (1.67 g.), m.p. 144-146 C., M1 -+24.8 (c 1, dimethylformamide).

. Analysis.-Found (percent): C, 63.0; H, 6.5; N, 16.1. C I-1 N requires (percent): C, 63.1; H, 6.5; N, 16.4.

(ii) N-(t-Butoxycarbonyl-L-histidyl)pyrrolidine.-A solution of t-butoxycarbonyl-L-histidine methyl ester (1.35 g.) and pyrrolidine (0.83 ml.) in methanol (4 ml.) was kept at room temperature for 12 days. Ether (5 ml.) was added, the mixture was filtered, the filtrate evaporated and the residue dissolved in IN hydrochloric acid (40 m1.). This solution was washed with ether, excess solid sodium hydrogen carbonate added, and the product extracted into ethyl acetate. The combined extracts were dried (Na SO and evaporated giving crude product (1.24 g.) as a gum. The desired product crystallised from ethanol/ether as colourless crystals (0.50 g.) m.p. 116-120 C., [04 -+22.0 (c 1, dimethylformamide).

Analysis.Found (percent): C, 58.0; H, 7.7; N, 17.9. C H N O requires (percent): C, 58.4; H, 7.8; N, 18.2. (iii) N (L- Histidyl)pyrroline dihydrochloride.(a) Hydrogen chloride in dioxan (4N, 25 ml.) was added to a solution of N-(t-butoxycarbonyl-L-histidyl)pyrrolidine (0.308 g.) in dioxan ml.) and methanol (3 ml.). After 45 minutes at room temperature, the mixture was evaporated, the residue precipitated from methanol with ether and washed, by decanting, with ether giving the product as a white amorphous powder (0.277 g.), [04 +8.5 (c 1, dimethylformamide).

(b) A solution of N-(benzyloxycarbonyl-L-histidyl)pyrrolidine (0.342 g.) in methanol ml.) and 6N hydrochloric acid (0.5- ml.) was hydrogenated at room temperature and atmospheric pressure for 17 hours over 10% palladium/charcoal (0.050 g.). The mixture was filtered (Celite), evaporated and the residue recrystallised from methanol/ether giving product (0.282 g.), m.p. 165 C. (decomp.), [0:1 :3 +8.0 (c 1, dimethylformamide).

(iv) Cycloypentauecarboxylic acid p-nitrophenyl ester.-N,N'-dicyclohexylcarbodiimide (8.24 g.) was added to a stirred solution of 'cyclopentane carboxylic acid (4.60 g.) and p-nitrophenol (5.56 g.) in ethyl acetate (50 ml.) at 0 C. and the reaction mixture was stirred overnight. The mixture was filtered, the urea washed with ethyl acetate, the filtrate and washings evaporated, dissolved in ether, filtered, evaporated and the crystalline residue recrystallised from 90% aqueous ethanol to give product (5.3 g.), m.p. 43-44 C.

Analysis.F0und (percent): C, 61.3; H, 5.5; N, 5.75. C H NO requires (percent): C, 61.3; H, 5.6; N, 6.0. f (v) N-(Cyclopentylcarbonyl-L-histidyl)pyrrolidine (cpc- His-pyr).Triethylamiue (0.28 ml.) and cyclopentanecarboxylic acid p-nitrophenyl ester (0.26 g.) were added to a stirred solution of N- (L-histidyl)-pyrrolidine dihydrochloride (0.270 g.) in dimethylformamide (2 ml.) at room temperature. The mixture was kept at 0 overnight, filtered, the triethylamine hydrochloride washed with dimethylformamide and the combined filtrate and washings (ca. 4.5 ml.) diluted with 5% (by volume) of water. This solution was put on a column of sulphoethyl Sephadex C-25 resin (25 g. weighed as moist resin; 5 cm. column) equilibrated with dimethylformamide.

The column was washed with 5% water in dimethylformamide to remove neutral and acidic co-products and was then eluted with 2.5% triethylamine, 9% water in dimethylformamide. Fractions containing product (as detected by TLC) were combined, evaporated and the residue triturated with ether giving crude product as a gum (0.200 g.). This was dissolved in dioxan, 4N hydrogen chloride in dioxan added and the precipitate washed with ether'by decanting,'dissolved in water, filtered and lyophilized giving the product as the hydrochloride (0.181 g.),- 2.0 (0 1,4, dimethylformamide).

Analysis.Found (percent): C, 53.5; H, 7.5; N, 15.4 C H N O HCl, H O requires (percent): C, 53.5; H, 7.6; N, 15.6. v

Investigations to determine the level of inhibition of the activity of TRH were carried out by a1nethod,:based on an assay of the activity of TRH of C. Y. Bowers ("Hypophysiotropic Hormones of the Hypothalausf The'Williams and Wilkins Co., 1970, p. Groups of mice' were fed on a low-iodine diet for two weeks, being kept an'n vironmental temperature of 14C. during the last four days, then 1 was given with triiodothyronine (usually 0.1,ug.) and 24 hours later the first blood sample (initial) was taken; samples of TRH, or sa1ine'(ascontrol) or of T RH followed immediately by'bpc-His-pyr '(ashydrochloride) were then administered intravenously and two hours later a second blood sample (final) was taken; blood.radio-* activities were measured in counts per minute (c.p.m.) and the response was expressed as Final Initial c.p.m. .100)

The results shown inTable I indicate a statistically sig-': nificant (P 0.01) decrease in the response to TRH when this is followed cpc-His-pyr (C). r 1 1 TABLE I When cpc-His-pyr (400 g.) was administered to two human subjects immediately before TRH (400 g.) the amounts of radioimmunoassayable TSH given in Table II were found in blood samples taken at the times indicated. The results of giving TRH (400 ,ug.) alone one week previously in the same subjects are also given in Table II.

TABLE II v TSH values uU/ml.) at the following times (minutes) after TRH injection 4 .4 12 .15 15113 '10 I9 3 a 5 7- a p e -2 2;? 8.8 .7- 4 4 W .4 5 .7 4.1%. .3

in which His is L-histidyl or a'pharrnaceiitically acceptable alt t f i 1" 1 1..: 2;. 232.1.

6 2. The compound of the formula References Cited UNITED STATES PATENTS 3,330,857 7/1967 Hess 260-309 5 OTHER REFERENCES in which His i L histidyl Guttmann: Chem. AbS., V01. 55, columns 23360-66 3. The hydrochloride of the compound of the formula (19 NATALIE TROUSOF, Primary Examiner '3His-N 1O 0 US. Cl. X.R.

. 260-"463 R; 424-473 1n WhlCh H1s 1s L-hlstldyl. 

